An applied electric field can be used to modulate a neuron' s activity. Although the advantage of employing fields for implementation in the design of neural prosthetics was recognized from invertebrate research, the field lay fallow for nearly a decade. Over the past five years, we have moved this field forward significantly. In recent papers, we have demonstrated that a DC electric field could be used to suppress or enhance epileptiform activity in hippocampal slices (Gluckman, et al., 1996a), and, when applied adaptively, could turn off seizures indefinitely (Gluckman, et al., 2001). One advantage of using electric fields to interact with neuronal networks is that, if properly instrumented, it can be done simultaneously with ongoing measurement of neuronal activity. Therefore, feedback can be easily implemented. But, one of the reasons electric fields have not been pursued is that readily available measurement and stimulation electronics are not easily adaptable for use with electric field stimulation. In addition, until recently, biocompatible electrode materials with sufficient charge passing capacity to produce sustained electric fields were not available. The aims of this project are to translate our existing seizure control techniques for chronic in vivo animal use. This will require design of instrumentation for simultaneously stimulating with electric fields and recording neuronal activity in intact brain, to establish safety limits for biocompatible electrodes under electric field stimulation, and to develop and test feedback seizure control algorithms. The instrumentation and methods developed will be prototypes of a novel neuronal interface based on electric field stimulation. Such an interface would lay the groundwork for a new generation of medical devices to treat dynamical diseases of the brain such as epilepsy, to provide an interface for neuronal prosthetics, as well as provide an arsenal of new tools for probing the complex dynamics of neuronal systems.